A one-way trip to Mars sounds like something you'd wish on your worst enemy — so why would more than 78,000 people from around the world pay up to $75 for a chance to die on another planet?

"I can say I have an ulterior motive," said David Brin, who has written more than a dozen science-fiction novels — including "The Postman," which was turned into a Kevin Costner movie in 1997. "I'd get a lot of writing done, and it might be memorable.".